The 2011 accident at the Fukushima Daiichi nuclear reactors in Japan spurred MIT scientists to advance accident-tolerant fuel (ATF) materials and fabrication processes. A 3D laser-induced chemical vapor deposition technique was developed for the production of uranium nitride fuel.

The method has been used to demonstrate a fuel-as-fiber concept in an ATF design that features high thermal conductivity, strong capability of radioactivity retention and requires relatively low enrichment levels with The ATF design provides an additional layer of containment while packing three to four times the fuel mass per volume as compared to competing fuel forms with similar safety characteristics. Source: Koroush Shirvan/MITuranium nitride as the fuel for light water reactors. The fuel components are layered: uranium nitride is coated with a soft buffer layer of porous carbon, which in turn is coated with a denser carbon layer and followed by high melting point silicon carbide. The resulting fuel bundles are vertically stacked and enclosed in a cladding composed of silicon carbide or other ATF material.

The process results in increased fuel density, which translates into improved fuel use efficiency. The silicon carbide-coated fuel cylinders encased in silicon carbide-clad fuel rods are expected to withtand temperatures up to 1,800° C, enabling safe reactor operation and retention of fuel radioactivity at higher power levels.

The new ATF technology might be used to retrofit existing nuclear power stations with safer materials and might find application in microreactor and nuclear space propulsion systems.